03 Radar Flashcards
ATPL RADIO
What does it mean if a transponder receives a P2 pulse which is stronger than P1 and P3 pulses?
The transponder responses will be suppressed for a short time interval.
When, and from which station, is a Special Position Identification (SPI) pulse sent?
From the aircraft transponder upon selection of the IDENT button by the pilot.
The main factor which determines the minimum range that can be measured by a pulsed radar is pulse:
length
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The minimum range of a radar is determined by the pulse length (or pulse width). Pulse repetition/recurrence frequency defines the maximum unambiguous range of a radar.
Which of the following equipments works on the interrogator/transponder principle?
Secondary Surveillance Radar (SSR)
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Secondary surveillance radar (SSR) use a transponder in the aircraft that replies to interrogation pulses from the ground station.
With regard to SSR
the interrogator is on the ground and the transponder is in the aircraft
Surface movement radar operates mainly in the SHF band as opposed to the EHF band. This is because:
EHF is absorbed and scattered by moisture in the air. Use of SHF reduces this problem
When both SSR and primary radar is presented on the controller’s display:
the primary radar information is more accurate in bearing and distance
In an Airborne Weather Radar that has a colour cathode ray tube (CRT) the areas of greatest turbulence are indicated on the screen by:
colour zones being closest together
Which of the following weather returns displayed on an Airborne Weather Radar should be avoided?
Fingers, Hooks, Scallops
Refer to the annex.
On control knob ‘3’, what does ‘MAP’ mode mean?
The ground/terrain will be displayed.
To improve the detection of precipitation area(s) in e.g. thunderstorms, in which the top of the cloud lies at or slightly above the level of flight,
the tilt setting should be lower when the aircraft climbs to a higher altitude.
In which mode of operation does the aircraft weather radar use a cosecant radiation pattern.
MAPPING
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The airborne weather radar use a cosecant square, fan shaped radiation pattern for ground mapping (up to approximately 70 nm range).
Considering a primary radar system, what kind of aerials are used?
One directional antenna both for transmitting and for receiving.
In order to be able to penetrate cloud, a primary radar signal must have:
a high frequency
What is the maximum number of Secondary Surveillance Radar (SSR) transponder codes in Mode A?
4096
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The secondary surveillance radar (SSR) transponder has a code selection of 0000 to 7777, where 0 to 7 gives 8 possible numbers, and four digits gives 84 = 4096 combinations.
A ground radar transmitting at a PRF of 1200 pulses/second will have a maximum unambiguous range of approximately:
67 NM
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To find the maximum unambiguous range for a radar based on PRF, the formula to use is:
Maximum Unambiguous Range = Speed of Light / 2 x PRF
MODE S
How does a ground interrogation signal (Mode A and C) get transmitted to a transponder?
in form of pairs of interrogative pulses with an additional control pulse.
In relation to primary radar, what does the term Pulse Recurrence Frequency signify?
The number of pulses transmitted per second.
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Pulse recurrence/repetition frequency (PRF) is the number of pulses transmitted per second. Pulse recurrence/repetition interval (PRI) is the time between two successive pulses.
Which one of the following Secondary Surveillance Radar (SSR) codes should be used by aircraft entering airspace from an area where SSR operation has not been required?
2000
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The SSR code ‘2000’ should be used by aircraft entering airspace from an area where SSR operation has not been required.
Airborne Weather Radar has been primarily developed to detect
the kinds of precipitation which are usually accompanied by turbulence.
A mode A/C transponder receives a P2 pulse from which the amplitude is larger than that of the P1 and P3 pulse. Why is this?
The transonder is located in the direction of one of the side lobes of the interrogator antenna.
Attenuation of radio waves means:
The weakening of the radiated waves
Which of the following equipment uses primary radar principles?
Airborne weather radar (AWR)
A frequency of 10 GHz is considered to be the optimum for use in an airborne weather radar system because:
the larger water droplets will give good echoes and the antenna can be kept relatively small
Ignoring pulse length and fly-back, a radar facility designed to have a maximum unambiguous range of 50 km will have a PRF (pulses per second) of:
3000
In relation to radar systems that use pulse technology, the term ‘Pulse Recurrence Rate (PRR)’ signifies the:
number of pulses per second
When an aircraft is operating its Secondary Surveillance Radar in Mode C an air traffic controller’s presentation gives information regarding the aircraft’s indicated flight level in increments of:
100 FT
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The transponder will send its altitude information in increments of 100s of feet in mode C.
A moving target indicator:
eliminates all stationary targets
The two main design functions of Secondary Surveillance Radar (SSR) Mode S are:
air to ground and ground to air data link communications and improved ATC aircraft surveillance capability
What information may be displayed on an ATC radar screen connected only to a primary radar system?
Aircraft position only.
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The primary radar is only able to indicate the position of the aircraft as it only rely on a echo from a target to paint a return without any further exchange of information.
In the Mapping Mode of an airborne weather radar which can utilise two different beam shapes, the:
fan-shaped beam effective up to a maximum of 50 NM to 60 NM range is used.
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The airborne weather radar use a cosecant square, fan shaped radiation pattern for ground mapping (up to approximately 70 nm range).
What type of beam is used by Airborne Weather Radar in weather mode?
3 – 5º Pencil beam
With SSR, interrogation and response signals:
are standard frequencies separated by 60 MHz
Mode A or C garbling may occur to:
Two or more aircraft in the same direction from the interrogator with a difference in slant range of less than 1.7NM
A weather radar, set to the 100 NM scale, shows a squall at 50NM. By changing the scale to 50 NM, the return on the radar screen should:
increase in area and move to the top of the screen
In Airborne Weather Radar (AWR), the main factors which determine whether a cloud will be detected are:
size of the water drops; wavelength/frequency used
Which statement is correct with respect to selections on the transponder control panel?
With ALT selected a reply in the modes A, C and S can be transmitted.
Which combination of characteristics gives best screen picture in a primary search radar?
short pulse length and narrow beam
The frequency of an SSR ground transmission is:
1030 +/- 0.2 MHz
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The secondary surveillance radar (SSR) will send its interrogation pulses at a frequency of 1030 MHz and the airborne transponder will reply at a frequency of 1090 MHz.
In general the operation of airborne weather radar equipment on the ground is:
only permitted with certain precautions, to safeguard health of personnel and to protect equipment
The selection of code 7500 on an aircraft SSR transponder indicates:
unlawful interference with the planned operation of the flight
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Transponder code 7500 is the international code for an aircraft experiencing unlawful interference (or hijacking).
The tilt angle of an Airborne Weather Radar (AWR) is set at +4°. If the beam width is 5° and the range of the cloud is 40 NM, what is the approximate height of the cloud above or below the aircraft when the weather return from the cloud just disappears from the screen?
6000 ft
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Ignoring pulse length, the maximum pulse repetition frequency (PRF) that can be used by a primary radar facility to detect targets unambiguously to a range of 200 NM is: (pps = pulses per second)
405 pps
In which frequency band do most airborne weather radars operate?
SHF
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Weather radars operate at frequencies of around 10 GHz which is in the SHF range (3 GHz – 30 GHz).
A frequency of airborne weather radar is:
9375 MHz
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The airborne weather radar normally use frequencies around 9 GHz (9000 MHz).
In an Airborne Weather Radar the areas of greatest turbulence are usually indicated on the screen by:
colour zones of red and magenta
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Areas of red signify areas of large droplets/wet particles indicating possible strong currents of air. For weather radars with turbulence detection, magenta will be used to indicate areas of possible turbulence/windshear within the cloud and also outside, based on the relative movement of the water droplets.
In an Airborne Weather Radar that has a colour cathode ray tube (CRT) increasing severity of rain and turbulence is generally shown by a change of colour from:
green to yellow to red
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Airborne weather radars will indicate the intensity of the precipitation or the size of the droplets as a range of colours, ranging from weaker to stronger:
- Green
- Yellow/amber
- Red
- Magenta
The “gain” control knob of an AWR adjusts:
the receiver sensitivity in order to achieve optimum target acquisition.
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The gain control of an airborne weather radar is used to adjust the sensitivity of the radar receiver and the higher the gain, the greater the sensitivity, i.e. any returns will be shown at a greater severity.
Which one of the following switch positions should be used when selecting a code on the transponder?
STBY (Standby)
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It is common practice to switch a transponder to STBY (Standby) before selecting a new SSR code.
In weather radar the use of a cosecant beam in ‘Mapping’ mode enables:
scanning of a large ground zone producing echos whose signals are practically independent of distance
MODE S
The allocation of 24-bit aircraft addresses is described in ICAO annex 10, it states that:
every aircraft will have been allocated with an ICAO Aircraft Address which is hard coded into the airframe.
A Primary radar operates on the principle of:
pulse technique
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Primary radar work on the principle of transmitting a pulse and receiving an echo back from a reflection of the pulse that was sent out. The amount of reflection depends on the frequency of the pulse and the nature of the object that created the reflection.
Which answer is correct concerning information determined and shown by ATC PSR (Primary Surveillance Radar) and SSR (Secondary Surveillance Radar) systems?
PSRs determine and show target range and bearing. SSRs determine and show target range, bearing, aircraft identification codes, aircraft altitude, selective addressing and full two-way data link.
The receiver in a primary radar:
all answers are correct
The magnetic heading of an aircraft is 040°. On the Airborne Weather Radar display the relative bearing of and the distance to the most southerly part of Lands End (approximate position: 50°03’N , 005°40’W) are, 030°R and 80 NM.
What is the position of the aircraft based on these observations?
The slant range correction and the map convergency between aircraft position and Lands End may be neglected.
(49°25’N , 007°30’W)
On the airborne weather radar display in WX mode, different colours are used:
to display different intensity of precipitation
The Moving Target Indication (MTI) in a primary radar has the following function:
Erase all stationary targets.
In a primary radar using pulse technique, the ability to discriminate between targets in azimuth is a factor of:
beam width